Measurement of factors affecting fit at the prosthetic socket-residual limb interface in people with transtibial amputation

Abstract

Many people with transtibial amputation rate the fit between their residual limb and prosthetic socket as the most important factor in the use of their prosthesis. Current research suggests that poor fit between the residual limb and the prosthetic socket can cause pain, skin breakdown or alteration of gait. This thesis focused on measurement methods to assess residual limb – prosthetic socket fit in people with transtibial amputation. Three aspects of fit were examined and new measurement methods for each aspect were explored. Fit affects the amount of relative movement that occurs between the residual limb and prosthetic socket. A method to measure this movement was proposed using motion capture analysis. The development and attempted validation of the method were outlined. Results were unpredictable and subject to confounding factors such as marker movement artefact. Therefore, the method was deemed not to be appropriate as a fit measurement tool in its current form. Based on these findings it was deemed necessary to investigate other measures of fit Fluctuation in residual limb volume can also affect fit. The reliability and validity of current residual limb volume measurement techniques were examined in a systematic review. Results demonstrated that circumferential measurements are the most reliable and valid tool currently available. The results from this review informed a study investigating the use of a low-cost optical scanner as a clinical volume measurement tool. Results found that the scanner was reliable when used by the same assessor but was not valid. The loading state at the prosthetic socket-residual limb interface is also an important factor in assessment of fit. The effect of pressure feedback to the prosthetist on the design of prosthetic sockets was assessed. It found that feedback resulted in reduction in pressure over anatomical regions of concern, and improved consistency between prosthetists. A new sensor to measure pressure and shear at the socket-limb interface was developed and benchtop testing was performed. These methods have the potential to aid in an improved understanding of the mechanisms that affect fit at the socket-limb interface of people with transtibial amputation. It is hoped that this can lead to improved fit and comfort for prosthetic users.